Stochastic Multiscale Fatigue Life Prediction Framework for Next Generation Durability and Damage Tolerance

Structural failure due to fatigue loading remains to be a tremendous concern for air- and spacecraft that operate in extremely harsh loading and environmental conditions. Initiation of fatigue cracks constitute a very significant portion of the overall life of metallic structural components especially under high cycle and very high cycle fatigue loading conditions. Despite this observation, current durability and damage tolerance approaches primarily rely on analysis of the long crack growth regime in the design, certification and maintenance of flight hardware with only empirical treatment of initiation. Fatigue crack initiation is significantly affected by the microstructural features of the material, and exhibits high degree of variability due to the random nature of the material microstructure. In order to overcome these challenges, this project will (1) establish predictive computational models for fatigue initiation life in metallic structures that directly incorporates features of the material microstructure; (2) quantify the role of microstructure induced uncertainties and sensitivities on the variability in fatigue crack initiation life; and (3) demonstrate the validity and feasibility of the computational approaches on metallic alloys of high relevance to NASA applications.

This project aims to achieve the ability to predict crack initiation life with the level of fidelity similar to that of the long crack growth regime. This project will facilitate risk-informed durability and damage tolerance based design including initiation regime and provide significant life extension of future air and space platforms and drastic reduction of weight in fatigue-critical structural components.

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